Creation of metastable defects in microcrystalline silicon films by keV electron irradiation

The effect of electron irradiation with 40 keV electrons on the sub-gap optical absorption, dark conductivity and photoconductivity of μc-Si:H films has been investigated. The experiments are carried out on undoped μc-Si:H film, prepared on quartz substrate by electron cyclotron resonance chemical vapor deposition (ECRCVD). The absorption coefficient in the sub-gap region (hv < 1.2 eV) as well as the photoconductivity of μc-Si:H films change considerably after electron irradiation. Annealing of the irradiated films for 1 h at 180 °C temperature restored the initial state. The observed parameter changes are attributed to the creation of metastable defects (silicon dangling bonds) in the disordered phase of the material near the surfaces of the microcrystalline columns in μc-Si:H films induced by electron irradiation. The inversely proportional dependence of photoconductivity on the concentration of these defects suggests that the dangling bonds created by electron irradiation are the dominant recombination centers in electron irradiated μc-Si:H films.